According to the same firm, while the EU vote in the UK is a relatively tight contest, it's a virtual certainty Scotland will vote to stay. It's 5/2 that Scotland votes to stay in the EU but the UK opts to leave.

Prime Minister David Cameron is confident the UK will vote to stay (Image: Reuters)

David Macdonald of Ladbrokes said: "Just when we thought we had put the Scottish Referendum vote to bed, it's resurfaced. With the possibility of the UK voting to leave the EU, this has rekindled interest in the betting and forced us to reopen the markets."